The U.N. human rights office said Monday's killing of 58 Palestinians by Israeli forces is "appalling" and it is worried what might happen on Tuesday and in the future.
Palestinian officials said more than 2,700 protesters were injured in clashes along the Gaza border during the deadliest day of cross-border violence since a 2014 war with Israel.
"It seems anyone is liable to be shot dead or injured: women, children, press, first responders, bystanders, and at almost any point up to 700 meters from the fence," the U.N. human rights office said Tuesday.
Israeli forces have faced criticism over the use of live fire to confront Palestinians at the border during demonstrations the past seven weeks, but Israeli officials say the actions are necessary to protect the border and accused Hamas militants of using protests as a cover to carry out attacks.
Israeli Prime Minister Benjamin Netanyahu said on Twitter Monday every country is obligated to defend its borders.
"The Hamas terrorist organization declares it intends to destroy Israel and sends thousands to breach the border fence in order to achieve this goal. We will continue to act with determination to protect our sovereignty and citizens," he said.
Monday's clashes occurred as U.S. and Israeli officials celebrated the opening of the new U.S. Embassy in Jerusalem. The Israeli military said more than 40,000 people protested.
Along with rejecting the U.S. Embassy move, Palestinians are protesting to mark the anniversary of what they call the "nakba" or "catastrophe" in reference to the hundreds of thousands of Palestinians who were expelled or fled during the 1948 war surrounding Israel's creation.
Some countries, including U.S. allies France and Britain, called for restraint on Israel's part to curb the bloodshed. But the United States did not join their call and laid the blame for the violence on the militant group Hamas that controls Gaza.
"We shouldn't lose sight that Hamas is responsible for the entire situation," White House spokesman Raj Shah said. He accused Hamas of "engaging in cynical action" against the Jewish state .
Palestinian President Mahmoud Abbas called the Israeli actions "massacres."
As the U.S. embassy was opened, U.S. President Donald Trump, in a video message, proclaimed Jerusalem as "the capital of Israel." Netanyahu declared, "We are in Jerusalem and we are here to stay."
Shah said the Gaza violence and the opening of the embassy in would not affect U.S. efforts to forge an Israel-Palestinian peace accord.
In his video remarks, Trump described the moving of the American diplomatic outpost to Jerusalem as "a long time coming." But the U.S. leader said the United States "remains committed to a lasting peace agreement" between Israel and the Palestinians.
Arab leaders condemned the U.S. action, with Lebanese Prime Minister Saad Hariri calling the embassy move "provocative" and Iranian Foreign Minister Javad Zarif describing it as "a day of great shame."
Abbas said he "will not accept" any peace deal with Israel that is proposed by the Trump administration.
European Union foreign policy chief Federica Mogherini called on Israel to respect the "principle of proportionality in the use of force" and should act "with utmost restraint to avoid further loss of life."
Israel sees all of Jerusalem as its capital, while most Palestinians hope to see East Jerusalem as the capital of a future Palestinian state.
Heather Murdock contributed to this report.